Accident sensor

ABSTRACT

An accident sensor for triggering a motor-vehicle safety system. A deformable, first part and a second part that acoustically detects a deformation at the first part is provided. The deformable, first part includes a plastic part or is integrated with a plastic part disposed around the exterior of the motor vehicle and includes a continuous medium for transmitting a signal. The first part generates an acoustical structure-borne signal when it is deformed. The second part includes a structure-borne signal sensor that receives the acoustical signal and conducts said signal further to an evaluation unit.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of Ser. No. 09/319,952 filed Sep.14, 1999.

BACKGROUND OF THE INVENTION

[0002] The invention relates to an accident sensor for detecting animpact.

[0003] The accident sensors currently used are designed as so-calledacceleration sensors. In the event of an accident, they detect theacceleration or deceleration that occurs' upon impact. If theacceleration or deceleration exceeds a critical value, motorvehiclesafety devices, such as seat-belt tighteners or airbags, are triggered.Usually, a plurality of acceleration sensors is mounted to the motorvehicle, with each acceleration sensor detecting the acceleration ordeceleration in one spatial direction for detecting a front or sideimpact, as well as rolling of the vehicle.

[0004] A disadvantage of these sensors is that an acceleration sensor isrequired for each spatial direction. Also, such sensors cannot determinethe site of the impact. These systems do not directly determine theimpact and the associated deformation of the motor vehicle, but only theacceleration or deceleration resulting from the deformation.

[0005] U.S. Pat. No. 4,346,914 discloses an impact-detection device thatresponds to acoustical oscillations in the bearing parts of the vehiclebody. The acoustical signals are converted into electrical signals byone or more piezoelectric force sensors that is or are connected to oneor more acoustical waveguides. The latter comprise thin steel tubes thatextend from the central installation point of the sensor(s) into theregions of the body that are at risk for impact, and serve there in theacoustical coupling with bearing parts that are spot-welded at numerouslocations. The signals are processed by a microprocessor. The signalprocessing constitutes the basis of the determination of an impactsituation that would require the triggering of the passenger-restraintsystem.

[0006] A disadvantage of this system is that the sound waves arecontained in a complicated tubular waveguide system, and transportedfrom there to a central piezo-element that converts the sound waves intoa voltage signal. This voltage signal is then conducted further to amicroprocessor. Not only is the processing of the tubular system complexand costly, but it is not possible to ascertain the origin of the signalwith this apparatus. It only recognizes the severity of the accident.The sensor cannot identify the site of the deformation.

[0007] DE 37 29 019 A1 describes a device for triggering a safetyapparatus. In this case, due to the association of sound and/orstructure-borne-sound sensors, a system is shifted in position fordifferentiating an impact against an obstacle from other, correspondingnoises and disturbances under critical driving conditions.

BRIEF SUMMARY OF THE INVENTION

[0008] It is the object of the invention to provide an accident sensorthat indicates the deformation of a motor vehicle upon impact against anobstacle, can be mounted simply and inexpensively, and identifies thedeformation site on the motor vehicle.

[0009] In accordance with the invention, the object is accomplished bythe features disclosed herein. The accident sensor acoustically,electrically or optically detects the material deformation occurringupon impact in a plastic part mounted to the exterior of the motorvehicle.

[0010] The advantages attained with the invention are that, first, theaccident sensor can detect the precise accident site on the motorvehicle. Furthermore, this solution is very inexpensive and simple incomparison to other accident sensors. Hence, the safety apparatuses canbe triggered more purposefully at no additional cost.

[0011] Advantageous modifications of the invention ensue. The plasticpart is disposed around the entire motor vehicle and servessimultaneously as a bumper and/or a scratch guard. Moreover, thedeformation site on the motor vehicle can be determined, particularlybased on the signal course and the determination of the transit time dueto the spatial orientation of the signal receivers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The figures illustrate embodiments of the invention. They showin:

[0013]FIG. 1: a motor vehicle having a peripheral plastic layer;

[0014]FIG. 2A: the measurement of the beam path in the plastic;

[0015]FIG. 2B: the optical accident detection based on a change in beampath;

[0016]FIG. 3A: the sound measurement on the plastic;

[0017]FIG. 3B: the acoustical accident detection based on materialcrackling;

[0018]FIG. 4A: plastic coated with a piezofilm;

[0019]FIG. 4B: the electromagnetic accident detection based on thedestruction of the piezofilm;

[0020]FIG. 5: a profile layer;

[0021]FIG. 6: a graphic representation of accident; and

[0022]FIG. 7: 7A and 7B: show a sensor integral with the plastic part.

DETAILED DESCRIPTION OF THE INVENTION

[0023]FIG. 1 shows a motor vehicle 1 having a peripheral plastic layer2. The illustrated motor vehicle 1 is completely or partiallyencompassed by plastic 2 in the impact regions. The plastic 2encompassing the motor vehicle 1 in the lower region in the applicationexample serves as a scratch guard and, in a minor rear-end collision orin the entrance or exit of a parking space, as impact protection forpreventing damage to the paint or the body. This plastic 2, which is thefirst part to be damaged in most accidents, is or contains at least onepart of the accident sensor. The plastic covering 2 can be disposedaround the entire vehicle 1 or only part of it. In any event, however,the plastic covering 2 serves numerous purposes.

[0024] The nature of the plastic 2 is such that it generates astructure-borne-sound signal during the deformation, or its radiationtransparency changes, or it generates an electrical signal by means ofan integrated piezo-layer. An advantage here is that plastic typicallypossesses far better structure-borne-sound properties than metal. Thus,the plastic protective covering 2 on the motor vehicle 1 can be usedsimultaneously as a deformation-measuring element that acousticallytransmits a material crackling that is typical for a specific degree ofdeformation, or optically or electrically transmits a different signal.The deformation site can be determined based on the transit timesrequired by the signal from the deformation site to the signal receiver.If the plastic is provided with profiles, for example, thestructure-borne-sound signal generated during the deformation is moreintensive and its measurement is less ambiguous, more exact andtherefore more useful.

[0025] The plastic covering 2 can also comprise numerous layerspossessing different properties, such as transparency or those of apiezo-layer.

[0026]FIG. 2A illustrates the principle of the measurement of theradiation or the beam path 5 in the plastic 2. This figure shows aradiation-transparent plastic 2 disposed around a motor vehicle, asdescribed in connection with FIG. 1. It is not crucial whether theentire plastic part 2 is radiation-transparent, or at least oneradiation-transparent layer is disposed on or in the plastic. Thestructure further includes a radiation source 3 and a radiation detector4. The radiation detector 4 measures the quantity of radiation or lightthat is transported from the radiation or light source via the lightguide. The light guide should be shielded such that no radiation that isincident from the outside can reach the radiation detector 4. As long asthe plastic part 2 is not damaged, the same quantity of light will reachthe radiation detector 4.

[0027]FIG. 2B shows the optical accident detection based on the changein beam path in the event that the plastic 2 and, particularly, thelight guide are damaged. During the deformation 10 of the plastic 2, thebeam path 5 changes, and the quantity of radiation that reaches theradiation receiver 4 is reduced. The radiation transmitted by theradiation or light source 3 takes a different path from the one shown inFIG. 2A. Thus, both the distribution and the quantity of the radiationdetected by the radiation detector 4 change. During the deformation 10of the plastic 2, these parameters change constantly until thedeformation process has ended. The change in the quantity of radiationover time, and the change in the radiation distribution over time, allowconclusions to be reached regarding the origin of the damage to theplastic. An evaluation electronics, not shown, and as disclosed in DE 3729 019, for example, determine the severity and source of the accidentand the deformation site on the motor vehicle.

[0028]FIG. 3A shows the acoustical sound measurement on the plastic. Amicrophone 6, particularly a structure-borne-sound sensor, a directionalmicrophone or another acoustical receiver, is disposed in the motorvehicle. The receiver is oriented toward the plastic 2. The sensitivityof the acoustical receiver lies in the range of the frequency spectrumof the structure-borne sound, particularly the material crackling of theplastic 2. The acoustical receivers 4 detect the acoustical signalsgenerated through the deformation of the plastic 2. One or morereceivers can be used for this purpose. The receivers can project indifferent spatial directions for using the transit time to determine theexact accident site. The signal is then conducted further via evaluationelectronics 13. DE 37 29 019 describes an example of this type ofelectronics.

[0029]FIG. 3B shows the acoustical accident detection through themeasurement of the structure-borne sound, particularly the materialcrackling. Structure-borne sound is generated during the deformation 10of the plastic 2. This initiates a material crackling 7 in theultrasonic range, which can be measured in the frequency range of 60 Hzto 100 Hz. A microphone 6 detects the intensity, phase position, dampingand transit time in the material crackling specific for this plastic 2.Evaluation electronics, not shown here, and disclosed in DE 37 29 019,for example, can use this data to determine the severity and origin ofthe accident, and the deformation site on the motor vehicle.

[0030]FIG. 4A shows the plastic 2 coated with a piezofilm 8. In thisembodiment, a piezofilm 8 is applied to the plastic 2 or integratedwith, the plastic 2. The piezofilm 8 generates an electrical or opticalsignal under pressure or the effect of a mechanical force. Furtherincluded in this arrangement is a receiver for detecting the electricalor optical signal. This receiver is not shown in the figure because itis disposed directly on the plastic in an optical detection arrangement,as shown in FIG. 2A, or, in an electrical detection arrangement, at anarbitrary location that is electrically connected to the piezofilm.

[0031]FIG. 4B shows the electromagnetic accident detection based on thedestruction of the piezofilm. During the deformation 10 or destruction,this piezofilm generates voltage signals or discharge flashes 11, whichcan be picked up by a detector. These signals are then conducted furtherto an evaluation unit, not shown, and evaluated there. An example ofsuch an evaluation circuit is disclosed in DE 37 29 019.

[0032]FIG. 5 shows different profiles 9. These profiles can be workedinto the plastic and/or the light guide for generating a betterstructure-borne-sound signal. If the piezofilm is applied to the plasticprovided with profiles, more voltage signals or discharge flashes aregenerated due to mechanical stresses than in an application to a smoothbase structure.

[0033]FIG. 6 illustrates the graphic representation of an accident. Thediagram shows the so-called material crackling. The amplitude, orintensity, indicates the degree of the deformation. Different accidentcharacteristics can be derived from the phase position and damping.Furthermore, the deformation site can be calculated through thedetermination of the transit time required by the sound signal fortraveling from the deformed plastic to the microphone.

[0034]FIGS. 7A and 7B show the sensors 6 integrated with the plasticpart 2.

[0035] The deformable first part 2 in FIGS. 2A, 2B, 3A, 3B, 4A and 4Beach constitutes a signal transmitting medium. After the signal iscreated during impact, the deformable first part transmits theacoustical, optical, or electrical signal over the medium to thereceiver.

[0036] In each of the embodiments discussed above, the deformable firstpart can either be distinct from or integral with the medium. Forexample, the deformable first part can be the plastic part and/or thecontinuous medium for transmitting a signal. Alternatively, the firstpart can be a distinct member attached to the plastic part.

[0037] In each of the embodiments discussed above, the impact site canbe determined based on the signal course over the medium. Any suitableevaluation unit, for example, a microprocessor, can be provided for thisfunction.

1. An accident sensor for triggering a motor-vehicle safety system,comprising: a deformable, first part and a second part that acousticallydetects a deformation at the first part, wherein the deformable, firstpart comprises a plastic part or is integrated with a plastic partdisposed around the exterior of the motor vehicle and includes acontinuous medium for transmitting a signal, wherein the first partgenerates an acoustical structure-borne signal when it is deformed, andwherein the second part comprises a structure-borne signal sensor thatreceives the acoustical signal and conducts said signal further to anevaluation unit.
 2. An accident sensor for triggering a motor-vehiclesafety system, comprising: a deformable, first part and a second partthat optically detects the deformation at the first part; wherein thefirst part comprises a radiation-transparent plastic part that ispenetrated by a defined quantity of light, is disposed on the exteriorof the motor vehicle, and includes a continuous medium for transmittinga signal; wherein a light beam path in the first part and the definedquantity of light change when the first part is deformed, said lightbeing a signal; and wherein the second part comprises aradiation-sensitive detector that detects said signal.
 3. The accidentsensor for triggering a motor-vehicle safety system, comprising: adeformable, first part and a second part that electromagneticallydetects the deformation at the first part; wherein the deformable, firstpart comprises a plastic part that is disposed on the exterior of themotor vehicle and includes a continuous medium for transmitting asignal, wherein said continuous medium generates pressure waves duringthe deformation; and wherein the second part comprises a piezofilm thatreceives the pressure waves and converts said pressure waves into anelectrical signal, and conducts said electrical signal further to anevaluation unit.
 4. The accident sensor for triggering a motor-vehiclesafety system according to claim 1, wherein the first part servessimultaneously as a bumper and a scratch guard for the motor-vehicle. 5.The accident sensor for triggering a motor-vehicle safety systemaccording to claim 1, further comprising an evaluation unit whichdetermines an impact site on the motor vehicle based on a signal coursebetween the impact site and a signal detector and a transit time elapsedbetween the signal being generated at the impact site and the signalbeing detected.
 6. The accident sensor for triggering a motor-vehiclesafety system according to claim 1, further comprising an evaluationunit which determines an impact site on the motor vehicle based on aspatial orientation of acoustical receivers.
 7. The accident sensor fortriggering a motor-vehicle safety system according to claim 2, whereinthe first part serves simultaneously as a bumper and a scratch guard forthe motor-vehicle.
 8. The accident sensor for triggering a motor-vehiclesafety system according to claim 3, wherein the first part servessimultaneously as a bumper and a scratch guard for the motor-vehicle. 9.The accident sensor for triggering a motor-vehicle safety systemaccording to claim 2, further comprising an evaluation unit whichdetermines an impact site on the motor vehicle based on a signal courseand a transit time between the impact site and a signal detection. 10.The accident sensor for triggering a motor-vehicle safety systemaccording to claim 3, further comprising an evaluation unit whichdetermines an impact site on the motor vehicle based on a signal courseand a transit time between the impact site and a signal detection. 11.The accident sensor for triggering a motor-vehicle safety systemaccording to claim 2, further comprising an evaluation unit whichdetermines an impact site on the motor vehicle based on a spatialorientation of acoustical receivers.
 12. The accident sensor fortriggering a motor-vehicle safety system according to claim 3, furthercomprising an evaluation unit which determines an impact site on themotor vehicle based on a spatial orientation of acoustical receivers.13. An accident sensor for triggering a motor-vehicle safety system,comprising: a deformable, first part and a second part that detects adeformation at the first part, wherein the first part comprises aplastic part or is integrated into a plastic part disposed around theexterior of the motor vehicle and includes a continuous medium fortransmitting a signal representing a deformation of the first part fordetection by the second part.
 14. The accident sensor according to claim13, wherein the continuous signal transmitting medium comprises a mediumfor transmitting an acoustical signal, the plastic part generates anacoustical structure-borne-sound when it is deformed that is transmittedover the medium, and the second part comprises a structure-borne-soundsensor that receives the acoustical signal and conducts it further to anevaluation unit.
 15. The accident sensor according to claim 13, whereinthe continuous signal transmitting medium comprises a radiationtransparent medium defining a beam path that is penetrated by a definedquantity of light, wherein the beam path and thus the defined quantityof light change when the plastic part is deformed, and the second partcomprises a radiation-sensitive detector that detects the quantity oflight, which has changed due to the deformation.
 16. The accident sensoraccording to claim 13, wherein the continuous signal transmitting mediumcomprises a medium for transmitting an electromagnetic signal, theplastic part includes means for generating an electromagnetic signalunder pressure, and the second part includes a detector for detectingthe electromagnetic signal transmitted over the medium by saidgenerating means.
 17. The accident sensor for triggering a motor-vehiclesafety system according to claim 1, further comprising an evaluationunit which determines an impact site on the motor vehicle based on aspatial orientation of optical receivers.
 18. The accident sensor fortriggering a motor-vehicle safety system according to claim 2, furthercomprising an evaluation unit which determines an impact site on themotor vehicle based on a spatial orientation of optical receivers. 19.The accident sensor for triggering a motor-vehicle safety systemaccording to claim 3, further comprising an evaluation unit whichdetermines an impact site on the motor vehicle based on a spatialorientation of optical receivers.